1. Field of the Invention
The present invention relates to a recording device. More particularly, the invention relates to a recording device which has a recording head including an array consisting of an N (N =a positive integer) number of dot forming elements, which are arrayed at a fixed spatial interval D in a secondary scanning operation as a recording-medium feeding direction, a head drive means for driving dot forming elements, a primary scan drive means for reciprocatively moving the recording head relative to a recording medium in a primary scanning operation, which is orthogonal to the secondary scanning operation, and a secondary scan drive means for feeding a recording medium relative to the recording head in the secondary scanning operation, wherein the recording head records an image while scanning a surface of a recording medium in primary and secondary scanning operations.
The present application is based on Japanese Patent Applications No. 2000-226277 and 2001-220944, which are incorporated herein by reference.
2. Description of the Related Art
A typical example of the recording method for improving the print quality of the ink jet printer is disclosed in Unexamined Japanese Patent Publication No. Hei. 9-169109. This recording method is constructed by combining a partial overlapping method into an xe2x80x9cinterlacing methodxe2x80x9d described in U.S. Pat. No. 4,198,642 and Unexamined Japanese Patent Publication No. Sho. 53-2040. The xe2x80x9cpartial overlapping methodxe2x80x9d is a recording method in which a part of a raster is recorded by using different inkjet nozzles (referred to simply as xe2x80x9cnozzlesxe2x80x9d) through a plural number of primary scanning operations, and another part of the raster is recorded by using one nozzle through one primary scanning operation. In the specification description, the raster which is recorded by using different nozzles through a plural number of primary scanning operations, will be referred to as an xe2x80x9coverlapping rasterxe2x80x9d, and the raster which is recorded by using one nozzle through one primary scanning operation, will be referred to as a xe2x80x9cnon-overlapping rasterxe2x80x9d.
In the overlapping raster, a plurality of nozzles used for raster formation are intermittently driven to eject ink drops. Accordingly, the recording head is driven at a drive frequency being different from that in the non-overlapping raster.
The recording head has a frequency characteristic proper to it. The frequency characteristic of the recording head may be expressed in the form of a characteristic variation of a quantity of an ink drop (ink ejection quantity) ejected from each nozzle of the recording head with respective to a drive frequency at which the recording head is driven. An example of the frequency characteristic of the recording head is shown in FIG. 3. In the graph, the abscissa represents a drive frequency (kHZ) and the ordinate represents an ink ejection quantity (ng=nano gram). As seen from the characteristic curve, to form dots at dot forming positions arrayed successively in the primary scanning operation, the recording head having that frequency characteristic is driven at a maximum drive frequency (=17 kHz) to eject ink drops, each of which has a quantity of 19 ng, from the nozzles to form dots at those positions. To form dots every other dot forming position, the recording head is driven at the half of the maximum drive frequency (=8.5 kHz), and a quantity of each of the ink drops ejected from the nozzles is 15.5 ng.
To form dots at dot forming positions arrayed successively, in the case of the non-overlapping raster, the recording head is driven at 17 kHz (maximum drive frequency) and causes it to eject ink drops each of 19 ng in quantity. In the case of the overlapping raster, to form dots every other dot by using two different nozzles, the recording head is driven at 8.5 kHz to eject ink drops each of 15.5 ng through the nozzles.
For this reason, where the recording head has the FIG. 3 frequency characteristic is used, the total ink ejection quantity of the non-overlapping raster is smaller than that of the overlapping raster. Where the ink quantity is small, the diameter of a formed dot is also small and sometimes, it is seen in different color under influence of other color dots. As a result, the overlapping raster is seen standing out of the non-overlapping raster. In other words, a stripe pattern appears on the picture. This problem is more serious as the number of the overlapping rasters successively formed increases.
Accordingly, an object of the present invention is to lessen such an unwanted phenomenon that the overlapping raster stands out of the non-overlapping raster in the partial overlapping recording method, and hence to improve the picture quality.
Another object of the present invention is to make inconspicuous the displacement of the dots from their proper positions, which is caused by a head movement error when the recording head is moved in the secondary scanning operation, in the interlacing method.
To achieve the above object, there is provided a first recording device having a recording head including an array consisting of an N (N=a positive integer) number of dot forming elements, which are arrayed at a fixed spatial interval D in a secondary scanning operation as a recording-medium feeding direction, a head drive means for driving dot forming elements, a primary scan drive means for reciprocatively moving the recording head relative to a recording medium in a primary scanning operation, which is orthogonal to the secondary scanning operation, and a secondary scan drive means for feeding a recording medium relative to the recording head in the secondary scanning operation, wherein the recording head records an image while scanning a surface of a recording medium in primary and secondary scanning operations, the improvement being characterized in that the secondary scan drive means determines a secondary scan distance of feeding the recording medium by one secondary scan drive so that the dot forming positions of an M (M=positive integer smaller than N/2) number of upstream dot forming elements, which are located in the upstream end of the dot forming element array as viewed in the secondary scanning operation, in a primary scanning operation, are coincident with the dot forming positions of an M number of downstream dot forming elements, which are located at the downstream end of the dot forming element array in a primary scanning operation after a predetermined number of primary scanning operations are performed, and the head drive means intermittently drives the upstream and downstream dot forming elements so as to form dots exactly at the dot forming positions on the same primary scan line, viz., without doubly forming the dots at the same dot forming position and the formation of no dot at its forming position, and drives the upstream dot forming elements so as to more frequently form the dot toward the upstream side and drives the downstream dot forming elements so as to more frequently form the dot toward the downstream side.
According to another aspect, there is provided a second recording device having a recording head including an array consisting of an N (N=a positive integer) number of dot forming elements, which are arrayed at a fixed spatial interval D in a secondary scanning operation as a recording-medium feeding direction, a head drive means for driving dot forming elements, a primary scan drive means for reciprocatively moving the recording head relative to a recording medium in a primary scanning operation, which is orthogonal to the secondary scanning operation, and a secondary scan drive means for feeding a recording medium relative to the recording head in the secondary scanning operation, wherein the recording head records an image while scanning a surface of a recording medium in primary and secondary scanning operations, the improvement being characterized in that the secondary scan drive means determines a secondary scan distance of feeding the recording medium by one secondary scan drive so that the dot forming positions of an M (M=positive integer smaller than N/2) number of upstream dot forming elements, which are located in the upstream end of the dot forming element array as viewed in the secondary scanning operation, in a primary scanning operation, are coincident with the dot forming positions of an M number of downstream dot forming elements, which are located at the downstream and of the dot forming element array in a primary scanning operation after a predetermined number of primary scanning operations are performed, and the head drive means intermittently drives the upstream and downstream dot forming elements so as to form dots exactly at the dot forming positions on the same primary scan line, viz., without doubly forming the dots at the same dot forming position and the formation of no dot at its forming position, and drives the upstream and downstream dot forming elements so as to more frequently form the dots as the upstream and downstream dot forming elements approach to common use dot forming elements other than the upstream and downstream dot forming elements.
In the first or second recording device, a recording medium is moved in the secondary scanning operation relative to the recording head, so that the dot forming positions of an M number of upstream dot forming elements are coincident with an M number of downstream dot forming elements. The upstream and downstream dot forming elements form dots exactly at the dot forming positions on the same primary scan line, viz., without doubly forming the dots at the same dot forming position and the formation of no dot at its forming position. Accordingly, an M number of primary scan lines (i.e., an M number of overlapping rasters) are formed by the dot forming positions of the M number of upstream dot forming elements and the M number of downstream dot forming elements.
An (Nxe2x88x922M) number of dot forming elements (referred to as xe2x80x9ccommon use dot forming elementsxe2x80x9d) other than the upstream and downstream dot forming elements are driven so as to form dots at all the position at which the dots should be formed. As a result, an (Nxe2x88x922M) number of non-overlapping rasters are formed.
The upstream dot forming elements are driven so as to more frequently form the dot toward the upstream side and the downstream dot forming elements are driven so as to more frequently form the dot toward the downstream side. In other words, the upstream and downstream dot forming elements are both driven so as to more frequently form the dot toward the common use dot forming elements. When the dot forming elements are more frequently driven, a chance of successively driving the dot forming elements also increases. As the dot forming elements are closer in their location to the common use dot forming elements, a frequency at which those elements are driven is closer to a frequency at which the common use dot forming elements are driven (In case of the ink jet printer stated in the related art description, the drive frequency is closer to or equal to that at which the common use dot forming elements are driven.).
Accordingly, as the M number of overlapping rasters is closer to the non-overlapping rasters, a dot diameter variation and a color variation, which are due to the difference between the element driving frequencies, become small in magnitude (in case of the ink jet printer stated in the related art description, the quantity of ejected ink becomes small or is equal to that by the common use dot forming elements). As a result, the phenomenon that the overlapping raster stands out of the non-overlapping raster, i.e., the stripe pattern, is made negligible in view, and this leads to picture quality improvement.
A part of the upstream dot forming element group located close to the common use dot forming elements in a primary scanning operation is coincident with a part (end side) of the downstream dot forming element group remote from the common use dot forming elements in another primary scanning operation performed after a predetermined number of secondary scan drives or secondary scanning operations. A part of the downstream dot forming element group located close to the common use dot forming elements is coincident with a part (end side) of the downstream dot forming element group remote from the common use dot forming elements in a primary scanning operation performed before a predetermined number of secondary scan drives. In other words, in the overlapping raster, the number of dots formed before the secondary scan drive increases as it is closer to the non-overlapping raster formed before the secondary scan drive. And, as it is closer to the non-overlapping raster formed after the secondary scan drive, the number of dots formed after the secondary scan drive increases. This feature achieves one of the objects of the invention, viz., to make inconspicuous the banding caused by the displacement of the dot forming positions in the secondary scanning operation after the secondary scan drive.
A third recording device is provided, which depends from the first or second recording device. In this recording device, P is mutually prime to xe2x80x9ckxe2x80x9d, and P+M=N, where P is an interlacing pitch having a value produced by dividing a secondary scan distance by the secondary scan drive means by a dot-to-dot distance xe2x80x9cdxe2x80x9d in a recording resolution R as viewed in the secondary scanning operation, and xe2x80x9ckxe2x80x9d is a dot forming element pitch xe2x80x9ckxe2x80x9d taking a value produced by dividing a spatial interval D among the dot forming elements by the distance xe2x80x9cdxe2x80x9d.
In the third recording device, the sheet feeding in the secondary scanning operation is carried out every unit distance in the interlacing method. Accordingly, the picture quality is improved in the interlacing method.
A fourth recording device is provided which depends from the first recording device. In this recording device, a sheet feeding pitch P is {2(Nxe2x88x92M)xe2x88x921}, and a dot forming element pitch xe2x80x9ckxe2x80x9d takes a value produced by dividing a spatial interval D among the dot forming elements by a dot-to-dot distance xe2x80x9cdxe2x80x9d in a recording resolution R as viewed in the secondary scanning operation, and the xe2x80x9ckxe2x80x9d is an even number, and the P is mutually prime to the xe2x80x9ckxe2x80x9d, the secondary scan drive means alternately and repeatedly causes a first secondary scan such that the recording medium is moved relative to the recording head in the secondary scan direction by the secondary scan distance of the dot-to-do distance xe2x80x9cdxe2x80x9d in a recording resolution R as viewed in the secondary scanning operation and a second secondary scan such that the recording medium is moved relative to the recording head in the secondary scanning operation by a distance of Pxc2x7d (P: sheet feeding pitch, d: do-to-dot distance in a recording resolution as viewed in the secondary scanning operation), in such a way that before the first secondary scan, the head drive means causes the dot forming element array to form dots on the recording medium, while the primary scan drive means causes the recording head to move in one of the forward and backward primary scanning operations, and after the first secondary scan, but before the second secondary scan, the head as drive means causes the dot forming element array to form dots on the recording medium, while the primary scan drive means causes the recording head to move in the other of the forward and backward primary scanning operations.
When the bidirectional recording is performed by the interlacing method, a raster formed before the movement of the secondary scan distance corresponding to the sheet feeding pitch P is different from a raster formed after the movement, in the raster forming direction. If the formation of the raster before the movement is performed by the forward primary scan, the formation of the raster after the movement is performed by the backward primary scan. In the recording head having a plurality of dot forming elements corresponding to a plurality of colors are arranged side by side in the primary scanning operation, when the raster forming directions are different, an order of colors printed by the forward primary scan is different from that by the backward primary scan. The color order difference produces the varying of color. As a result, a stripe pattern appears every secondary scan feeding, sometimes.
In the fourth recording device, two linear rasters formed before and after the first secondary scan are adjacent to each other, and formed by one and the same dot forming element. Thereafter, the sheet is fed, by the second secondary scan, in the secondary scanning operation by a distance (Pxc2x7d) which is obtained by multiplying the sheet feeding pitch P (=2(Nxe2x88x92Mxe2x88x921) by the dot-to-do distance xe2x80x9cdxe2x80x9d in the recording resolution as viewed in the secondary scanning operation. Subsequently, two linear rasters are formed again before and after the first secondary scan. In this way, the recording on the recording medium is performed every unit raster, which consists of the paired linear rasters formed by the forward and backward primary scans. Accordingly, the whole picture recorded is the aggregate of those unit rasters each consisting of the paired linear rasters. The directions of forming the paired linear rasters are always one direction (e.g., forward direction) and the other direction (e.g., backward direction). Accordingly, if those two linear rasters are handled as a unit, the raster forming directions are the same.
As a result, the whole picture is free from the stripe pattern, which inevitably appears every movement unit of the secondary scanning operation in the bidirectional recording by conventional interlacing method.
Each of the linear rasters is formed by one and the same dot forming element and by the forward or backward primary scan. Accordingly, the printing speed is higher than in the conventional full overlapping recording method.
If the dot diameter is about two times as large as the produce of multiplying the rater-to-raster distance xe2x80x9cdxe2x80x9d by {square root over (2)}, the theory allows the recording to be performed without producing a gap between the adjacent linear rasters formed by the dot forming elements (the sheet background appears in the form of stripe between the adjacent linear rasters, called a white stripe). In actual devices, the dot diameter is selected to be two times as long as the raster-to-raster distance xe2x80x9cdxe2x80x9d, allowing for the deflection of the dot forming element in the secondary scanning operation (called the bending of an ink flight).
In the fourth recording device, one and the same dot forming element is used for forming the paired linear rasters (which form one unit raster). Accordingly, even if the ink flight bending to the secondary scanning operation occurs in the formation of the paired linear rasters, the resultant linear rasters are likewise affected in their configuration by the flight bending. Accordingly, if the dot diameter substantially reaches a theoretical value (rater-to-raster distance xe2x80x9cdxe2x80x9d x 2xc2xd, 2xc2xd is hereinafter referred to as xe2x80x9c{square root over (2)}xe2x80x9d), no gap between both the linear rasters will be formed. Accordingly, even when the invention is applied to an ink jet printer using a pigment ink or inks whose dot diameter is smaller than a value two times as large as the rater-to-raster distance xe2x80x9cdxe2x80x9d, no stripe will be produced between those paired linear rasters.
The present invention also provides a fifth recording device which depends from the first recording device. In this recording device, a sheet feeding pitch P is {2(Nxe2x88x92M)xe2x88x921}, and a dot forming element pitch xe2x80x9ckxe2x80x9d takes a value produced by dividing a spatial interval D among the dot forming elements by a dot-to-dot distance xe2x80x9cdxe2x80x9d in a recording resolution R as viewed in the secondary scanning operation, and the xe2x80x9ckxe2x80x9d is an even number, and the P is mutually prime to the xe2x80x9ckxe2x80x9d, and the secondary scan drive means alternately and repeatedly causes a first secondary scan such that the recording medium is moved relative to the recording head in the secondary scanning operation by the dot-to-dot distance xe2x80x9cdxe2x80x9d in a recording resolution R as viewed in the secondary scanning operation and a second secondary scan such that the recording medium is moved relative to the recording head in the secondary scanning operation by a distance of Pxc2x7d (P: sheet feeding pitch, d: dot-to-dot distance in a recording resolution as viewed in the secondary scanning operation), in such a way that before the first secondary scan, the head drive means causes the dot forming element array to form dots on the recording medium, while the primary scan drive means causes the recording head to move in the forward or backward primary scanning operation, and after the first secondary scan, but before the second secondary scan, the head drive means causes the dot forming element array to form dots on the recording medium, while the primary scan drive means causes the recording head to move in the forward or backward primary scanning operation.
The fifth recording device is capable of recording a picture as the aggregate of unit rasters each consisting of the paired linear rasters, as a matter of course. One and the same dot forming element is used for forming the paired linear rasters (which form one unit raster). Accordingly, even if the ink flight bending to the secondary scanning operation occurs in the formation of the paired linear rasters, the resultant linear rasters are likewise affected in their configuration by the flight bending. For this reason, no stripe pattern will be produced between the paired linear rasters formed if the dot diameter is equal to its theoretical value or so. Accordingly, even when the invention is applied to an ink jet printer using a pigment ink or inks, no stripe will be produced between those paired linear rasters.
A sixth recording device of the invention depends from the fourth or fifth recording device. In this recording device, the primary scan drive means, the secondary scan drive means and the head drive means are arranged such that two linear rasters formed by one and the same dot forming element before and after the sheet feeding of the secondary scan distance xe2x80x9cdxe2x80x9d are handled as a unit raster, and a linear raster adjacent to the unit raster is formed by a dot forming element which is different from the dot forming element used for forming the unit raster.
A seventh recording device depends from the fourth or fifth recording device. In this recording device, an offset a of the secondary scan distance is larger than zero (0), but smaller than a value obtained in a manner that the product of multiplying the distance xe2x80x9cdxe2x80x9d by, {square root over (2)}is subtracted from a diameter of a dot formed by the dot forming element, and the result of the subtraction is divided by {square root over (2)}, and the first secondary scan distance is the sum of the distance xe2x80x9cdxe2x80x9d and the offset xcex1, and the second secondary scan distance is the result of subtracting the offset from the distance (Pxc2x7d).
If the paired linear rasters are affected in their formation by the ink flight bending of the dot forming element used, the resultant linear rasters are likewise affected in its configuration by the flight bending. Accordingly, a distance xe2x80x9cxxe2x80x9d between both the linear rasters is reduced to such a level as defined by the result of dividing the actual dot diameter xe2x80x9caxe2x80x9d by {square root over (2)}. In other words, even if the actual dot diameter xe2x80x9caxe2x80x9d takes its theoretical value (=x x {square root over (2)}) relative to the raster-to-raster (, or dot-to-dot) distance xe2x80x9cxxe2x80x9d, a white stripe does not appear between the linear rasters in the recording.
Accordingly, the recording is performed without producing the stripe between the linear rasters if the raster-to-raster distance xe2x80x9cxxe2x80x9d is defined by
D less than xxe2x89xa6d+xcex1MAX
where xcex1MAX: maximum value of the offset xcex1 which is added to the raster-to-raster distance.
However, even if xcex1MAX is set as follows, the printing may be performed without producing a white stripe between the adjacent linear rasters.
xcex1MAX={axe2x88x92dxc3x97{square root over (2)}}÷{square root over (2)}
where a: actual dot diameter
If the offset xcex1 is selected so as to satisfy D less than xcex1xe2x89xa6xcex1MAX, the distance between the rasters formed by the same dot forming element is (d+xcex1). Accordingly, in one gap between the linear rasters no white stripe appears. Another gap between the linear rasters is expanded, and hence even if the dot diameter xe2x80x9caxe2x80x9d of an ink drop ejected from the nozzle is relatively small, a width in a picture (line width) in a picture formed by the paired linear rasters may be increased.
The raster-to-raster distance after the sheet is moved by the secondary scan distance Pxc2x7d is reduced by xcex1. The linear rasters formed before the feeding of the secondary scan distance it (Pxc2x7dxe2x88x92xcex1) is formed by a dot forming element different from that used for forming the linear rasters after the movement of the secondary scan distance (Pxc2x7dxe2x88x92xcex1). Therefore, even in a case where a stripe pattern will be formed unless the actual dot diameter=two times as long as the distance xe2x80x9cdxe2x80x9d, no white stripe patter is formed between the white linear rasters if the dot diameter  less than 2d, since the secondary scan distance is selected to be smaller than the distance xe2x80x9caxe2x80x9d, by xcex1. Accordingly, no white stripe is formed in both the gaps between the paired linear rasters by one dot forming element and between the paired linear rasters by another dot forming element.
A specific value of xcex1 is preferably determined, every recording device, by the experiment or the like so that no stripe appears between the paired linear rasters formed before and after the sheet is moved by a secondary scan distance (d+xcex1) and between the paired linear rasters formed before and after the sheet is moved by a secondary scan distance (121d+xcex1).
An eighth recording device depends from the fourth or fifth recording device. In this recording device, the first secondary scan distance is the sum of the distance xe2x80x9cdxe2x80x9d and an offset xcex1, and the second secondary scan distance is the result of subtracting the offset from the distance (Pxc2x7d), and the offset xcex1 is larger than 0, and takes such a value as not to generate a white stripe pattern between adjacent linear rasters formed before and after the sheet feeding of the secondary scan distance (d+xcex1) and between adjacent linear rasters formed before and after the sheet feeding of the secondary scan distance {(Pxc2x7d)xe2x88x92xcex1}.
A ninth recording device also depends from the fourth or fifth recording device. In this recording device, recording data to form dots in the primary scanning operation before the first secondary scan is set or may be set to be the same as recording data to form dots in the primary scanning operation after the first secondary scan.
A tenth recording device depends from the fourth or fifth recording device. In this recording device, recording data to form dots in the primary scanning operation before the first secondary scan is set or may be set to be the same as recording data to form dots in the primary scanning operation after the first secondary scan.
An eleventh recording device has a recording head including an array consisting of an N (N=a positive integer) number of dot forming elements, which are arrayed at a fixed spatial interval D in a secondary scanning operation as a recording-medium feeding direction, a head drive means for driving dot forming elements, a primary scan drive means for reciprocatively moving the recording head relative to a recording medium in a primary scanning operation, which is orthogonal to the secondary scanning operation, and a secondary scan drive means for feeding a recording medium relative to the recording head in the secondary scanning operation, wherein the recording head records an image while scanning a surface of a recording medium in primary and secondary scanning operations. The eleventh recording device is improved in that the secondary scan drive means determines a secondary scan distance of feeding the recording medium by one secondary scan drive so that the dot forming positions of one upstream end of the dot forming element array as viewed in the secondary scanning operation, in a primary scanning operation, are coincident with the dot forming positions of one downstream dot forming element, which are located at the downstream end of the dot forming element array in a primary scanning operation after a predetermined number of primary scanning operations are performed, and the head drive means intermittently drives the upstream and downstream dot forming elements so as to successively form dots in a ratio of 1 to 1 on the same primary scan line, and the number of dots successively formed is selected so as to make inconspicuous the displacement of the dot forming positions for the upstream dot forming element relative to the dot forming positions for the downstream dot forming element, if the displacement is present.
In the eleventh recording device, the upstream dot forming element and the downstream dot forming element form dots in a ratio of 1 to 1 in number, and those dots are successively formed. The number of those dots formed in succession is selected so that the displacement of the dot forming positions for the upstream and downstream dot forming elements in the secondary scanning operation is inconspicuous.
Accordingly, if the diameter of each dot forming the overlapping raster is small, and its color is seen different from its original one, the color difference is negligible in view since one overlapping raster is used.
As recalled, the upstream dot forming element and the downstream dot forming element form dots in a ratio of 1 to 1 in number, and those dots are successively formed a dot diameter variation and a color variation, which are due to the difference between the element driving frequencies, become small in magnitude (in case of the ink jet printer stated in the related art description, the quantity of ejected ink becomes small or is equal to that by the common use dot forming elements). As a result, the phenomenon that the overlapping raster stands out of the non-overlapping raster, i.e., the stripe pattern, is made negligible in view, and this leads to picture quality improvement.
The number of those dots formed in succession by the upstream dot forming elements and the downstream dot forming elements is selected so that the displacement of the dot forming positions for the upstream and downstream dot forming elements in the secondary scanning operation is inconspicuous. This feature makes inconspicuous the banding caused by the displacement of the dot forming positions in the secondary scanning operation after the secondary scan drive.
A twelfth recording device depends from the eleventh one. In this recording head xe2x80x9ckxe2x80x9d is an even number, P is mutually prime to xe2x80x9ckxe2x80x9d, and P+1=N, where P is a sheet feeding pitch having a value produced by dividing a secondary scan distance by the secondary scan drive means by a dot-to-dot distance xe2x80x9cdxe2x80x9d in a recording resolution R as viewed in the secondary scanning operation, and xe2x80x9ckxe2x80x9d is a dot forming element pitch xe2x80x9ckxe2x80x9d taking a value produced by dividing a spatial interval D among the dot forming elements by the distance xe2x80x9cdxe2x80x9d.
In the twelfth recording device, the feeding in the secondary scanning operation is performed every unit distance in the interlacing method. In this respect, the picture quality is improved in the interlacing method.
A thirteenth recording device depends from the eleventh one. In this device, a sheet feeding pitch P is 2Nxe2x88x923, and a dot forming element pitch xe2x80x9ckxe2x80x9d takes a value produced by dividing a spatial interval D among the dot forming elements by a dot-to-dot distance xe2x80x9cdxe2x80x9d in a recording resolution R as viewed in the secondary scanning operation, and the xe2x80x9ckxe2x80x9d is an even number, and the P is mutually prime to the xe2x80x9ckxe2x80x9d, the secondary scan drive means alternately and repeatedly causes a first secondary scan such that the recording medium is moved relative to the recording head in the secondary scanning operation by the secondary scan distance in a recording resolution R as viewed in the secondary scanning operation and a second secondary scan such that the recording medium is moved relative to the recording head in the secondary scanning operation by the secondary scan distance obtained by multiplying the sheet feeding pitch P by a recording resolution as viewed in the secondary scanning operation, in such a way that before the first secondary scan, the head drive means causes the dot forming element array to form dots on the recording medium, while the primary scan drive means causes the recording head to move in one of the forward and backward primary scanning operations, and after the first secondary scan, but before the second secondary scan, the head drive means causes the dot forming element array to form dots on the recording medium, while the primary scan drive means causes the recording head to move in the other of the forward and backward primary scanning operations.
The thirteenth recording device produces useful effects comparable with those by the thirteenth recording device,
A fourteenth recording device depends from the eleventh recording device. In this recording device,a sheet feeding pitch P is 2Nxe2x88x923, and a dot forming element pitch xe2x80x9ckxe2x80x9d takes a value produced by dividing a spatial interval D among the dot forming elements by a dot-to-dot distance xe2x80x9cdxe2x80x9d in a recording resolution R as viewed in the secondary scanning operation, and the xe2x80x9ckxe2x80x9d is an even number, and the P is mutually prime to the xe2x80x9ckxe2x80x9d, the secondary scan drive means alternately and repeatedly causes a first secondary scan such that the recording medium is moved relative to the recording head in the secondary scanning operation by the secondary scan distance in a recording resolution R as viewed in the secondary scanning operation and a second secondary scan such that the recording medium is moved relative to the recording head in the secondary scanning operation by the secondary scan distance obtained by multiplying the sheet feeding pitch P by a recording resolution as viewed in the secondary scanning operation, in such a way that before the first secondary scan, the head drive means causes the dot forming element array to form dots on the recording medium, while the primary scan drive means causes the recording head to move in the forward or backward primary scanning operation, and after the first secondary scan, but before the second secondary scan, the head drive means causes the dot forming element array to form dots on the recording medium, while the primary scan drive means causes the recording head to move in the forward or backward primary scanning operation.
A fifteenth recording device depends from the thirteenth or fourteenth recording device. In this device, means and the head drive means are arranged such that two linear rasters formed by one and the same dot forming element before and after the sheet feeding of the secondary scan distance xe2x80x9cdxe2x80x9d are handled as a unit raster, and a linear raster adjacent to the unit raster is formed by a dot forming element which is different from the dot forming element used for forming the unit raster.
A sixteenth recording device depends from the thirteenth or fourteenth recording device. In this recording device, an offset xcex1 of the secondary scan distance is larger than zero (0), but smaller than a value obtained in a manner that the product of multiplying the distance xe2x80x9cdxe2x80x9d by {square root over (2)} is subtracted from a diameter of a dot formed by the dot forming element, and the result of the subtraction is divided by {square root over (2)}, and the first secondary scan distance is the sum of the distance xe2x80x9cdxe2x80x9d and the offset xcex1, and the second secondary scan distance is the result of subtracting the offset from the distance (Pxc2x7d).
The sixteenth recording device produces useful effects comparable with those by the seventh recording device.
A seventeenth recording device depends from the thirteenth or fourteenth recording device. In this recording as device, the first secondary scan distance is the sum of the distance xe2x80x9cdxe2x80x9d and an offset xcex1, and the second secondary scan distance is the result of subtracting the offset from the distance (Pxc2x7d), and the offset xcex1 is larger than 0, and takes such a value as not to generate a white stripe pattern between adjacent linear rasters formed before and after the sheet feeding of the secondary scan distance (d+xcex1) and between adjacent linear rasters formed before and after the sheet feeding of the secondary scan distance {(Pxc2x7d)xe2x88x92xcex1}.
An eighteenth recording device depends from the thirteenth or fourteenth recording device. In this recording device, recording data to form dots in the primary scanning operation before the first secondary scan is set or may be set to be the same as recording data to form dots in the primary scanning operation after the first secondary scan.
A nineteenth recording device depends from-the sixth device. In this recording device, recording data to form dots in the primary scanning operation before the first secondary scan is set or may be set to be the same as recording data to form dots in the primary scanning operation after the first secondary scan.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.